The present invention relates to a shift control device of an automatic transmission which is equipped with a manual shift mode, which may be installed in automotive vehicles.
Conventionally, the automatic transmission for automotive vehicles which is equipped with the automatic shift mode, in which a shift gear is selected automatically depending on vehicle traveling states, and the manual shift mode, in which the shift gear is selected by a manual operation of a driver, has been used widely.
A shift operating portion 20 for a range selection of this kind of automatic transmission has M range of the manual shift mode, in addition to P range for parking, R range for reversing, N range for neutral, and D range for forwarding of the automatic shift mode (see FIG. 2A).
When the driver operates a shift lever 21 to D range, the forward traveling of the vehicle with the automatic shift mode can be provided. Meanwhile, when the shift lever 21 is shifted to M range by the driver, the manual mode is selected. In the manual mode, the shift-up operation of gear is achieved by pushing the shift lever 21 downward, i.e., toward the “+” side (FIG. 2B), while the shift-down operation of gear is achieved by pushing the shift lever 21 upward, i.e., toward the “−” side (FIG. 2B).
Herein, according to the above-described automatic transmission equipped with the manual mode, the shift control is configured to execute the shift-up control automatically even in case of the manual mode when a preset limit speed A of the engine is detected in order to prevent the over-revolution state of the engine which may increase over the engine's limit speed L and cause some damage to the engine (see FIG. 5).
However, there is a concern that this automatic shift-up control would give the driver unconformable driving feelings because of its unexpected shift to the driver, and would cause the unstable vehicle driving because the driving force could not be ensured as the driver had expected.
Moreover, there is a problem in that in case the above-described automatic shift-up control and the manual shift-up operation are conducted almost at the same time and they are overlapped, for example, a two-stage shift-up of gears would occur. Herein, Japanese Patent Laid-Open Publication No. 2007-315414 discloses the gear shift control device in which the manual shift-up operation is restricted when the automatic shift-up control is commanded to prevent the two-stage shift-up of gears, so that the unexpected shift-up can be prevented.
Herein, since in general some appropriate operational time T may be required during a period of time from a shift-up shift start S to a shift completion E for the above-described automatic transmission which can avoid the engine's over revolution, the above-described preset limit engine speed A is set to be lower than the above-described engine's limit speed L so that the engine speed does not exceed the engine's limit speed L even if the engine speed increases during the operational time T (see FIG. 5).
There was a problem in that, for example, even in case the driver operated the accelerator so as to be closed during the period of time from the detection of the preset limit speed A which is lower than the engine's limit speed L to the shift-up completion E in order to avoid the over revolution, if the shift-up of gear was executed by the automatic shift-up control, the reduction of driving force by this shift-up would occur in addition to the reduction of driving force by the driver's closing the accelerator and thereby an unexpected large reduction of driving force would occur, so that the driver could not obtain the driving force which the driver had expected